Drugmakers struggle to get volunteers for COVID-19 vaccine clinical trials as more people opt for approved shots

As more COVID-19 vaccines are authorized and made available to a broader population of people, drugmakers are struggling to conduct further studies of the vaccines, The Wall Street Journal reported.

Many people don't want to take a placebo, according to the newspaper, but drugmakers still need trials to answer such questions as whether a half-dose of a vaccine is effective and whether vaccines work in different populations.